High speed punch



May 23, 1961 H. A. PANISSIDI HIGH SPEED PUNCH 4 Sheets-Sheet 1 Filed Nov. 20, 1957 L F I ZOE-4km 4 Sheets-Sheet 2 Filed Nov. 20, 1957 HUGO A. PANISSIDI his ATTORNEYS.

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INVENTOR. FIG- HUGO A. PANISSIDI BY W x MM his ATTORNEYS.

May 23, 1961 2,985,237

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United States Patent HIGH SPEED PUNCH Hugo A. Panissidi, Poughkeepsie, N .Y., assignor to International Business Machines Corporation, New York, N.Y., a corporation of New York Filed Nov. 20, 1957, Ser. No. 697,600

20 Claims. (Cl. 234-109) The present invention, generally, relates to punching apparatus and, more particularly, to a new and improved fluid operated apparatus for the punching of cards at a high speed.

A punching apparatus of the type to which the invention relates is particularly suited for the punching of holes to represent information in record or tabulating cards. The location of each hole punched is predetermined in accordance with the information it is to represent.

. Past etforts to increase the operating speed of punching apparatus have produced speeds of approximately 500 cards per minute. Such apparatus as heretofore known are mechanically operated and, thus, possess certain inherent limitations such as, for example, a low force-to-mass ratio, excessive impacts developed at high speeds in levers, linkages and pivots and the difiiculty in maintaining proper lubrication to prevent excessive wear. Attempts have been made to minimize these disadvantages by providing various refinements ,to permit greater precision of manufacture, but the 500 cards per minute has come to be recognized as a practical limit with such apparatus.

It is an object of this invention to provide a card punching apparatus which permits the punching of record cards at a higher speed than is possible with apparatus of the type heretofore known.

A further object of the invention is to provide a new and improved card punching apparatus which overcomes the above-mentioned disadvantages.

Another object of the invention is to provide a card punching apparatus of a new and improved construction which is operable by hydraulic or fluid pressure.

Generally, the invention in its preferred form is embodied in a unique structure such that the number of moving mechanical parts is reduced to a minimum and the speed of operation is increased substantially. Each of a plurality of punching members is communicated with a fiuid to which pressure is alternately applied and released according to a selected timing schedule. An electromagnetic means determines automatically predetermined ones of the punching members to be actuated as the pressure portion of the timing cycle is traversed. In this manner, the number of cards punched per minute is more than double the number punched by apparatus heretofore known.

The various novel features of construction, combination and relation of parts by which the foregoing and other objects are attained, are set forth in detail in the following specification.

The drawings accompanying and forming part of the specification illustrate one practical embodiment of the invention as applied to high speedpunching of record or tabulating cards. It should be understood, however, that the invention is not limited to this use or to this particular form of structure, as will appear from the scope of the appended claims.

In the drawings:

Figure l is a side elevational view of a card punching 2,985,237 Patented May 23, 1961 'ice 2 apparatus embodying the novel features of the invention; Figure 2 is a view in vertical section taken along the ine 22 of Figure 1;

Figure 3 is a view in vertical section taken along the line 3-3 in Figure 2;

Figure 4 is a plan view showing the arrangement of the punch die for the various punching members of the two stations shown in Figure 1;

Figure 5 is a timing chart showing the relative co-op eration of various operating components of an apparatus constructed in accordance with the invention; and

Figure 6 is a fragmentary plan view of a punched record card showing the relative spacing of the various zine 12 for containing a plurality of cards to be punched.

In the particular magazine 12 illustrated, the blank cards 13 are fed at high speed from the bottom by any suitable means, represented generally by a lever 14 pivotable about an axis 15 such that the opposite end 16 is in contact with the lowermost card in the magazine.

When the lever 14 is rotated about the axis 15 in a counterclockwise direction, the end 16 pushes the lowermost card of the plurality 13 into engagement with co-' operating feed rolls 17 and 18 which rotate as indicated by an arrow on each roll. ing feed rolls 19 and 20 receive each unpunched card from the first feed rolls 17 and 18 and forward it to the punching apparatus 10.

In many instances, it is desirable to have a sensing de-* vice for such purposes as counting or signalling. Such a sensing device in this instance may be positioned between the first and second feed rolls and is indicated diagrammatically by the numeral 21, Figure 1.

Each card that is fed to the apparatus 10 by the second feed rolls 19 and 20 is gripped by co-operating belt meanswhich grip the ends of each card as best illustrated'in Figure 2 of the drawings by the two upper belts 22 and 23 and the co-operating lower belts 24 and 25, respectively. The card being gripped in Figure 2 is indicated by the numeral 26. Of course, it is to be understood that any other suitable means may be used to convey each card to be punched through the apparatus 10, the belt means being indicated here merely for illustrative purposes.

As each card moves into the punch apparatus 10, it comes to rest against any suitable positioning member 38 which stops the card momentarily for the punching operation. During this punching period which is in the order of six milliseconds or less, the card is held firmly by the belts sliding over the ends and keeping the card against the member 38.

After the cards have been punched in the apparatus 10, they are ejected into a suitable receptacle 27. It should also be understood that the receptacle 27 is merely a diagrammatic illustration, it being obvious that any other receptacle means may be used, such as a moving conveyor, a chute, or the like.

In the particular embodiment of the invention illustrated in Figure 1, it is desired to provide 960 separate punching members. It has been found that with this stations permits a more simplified punching -die con- A second pair of co-operat-' assess? struction, each die containing provisions for 480 punching members. The spacing of these punching dies is best illustrated in Figure 6 of the drawings which shows a typical tabulating card 31 with a plurality of holes punched therein. Now, byway of example, the hole 31 in column 1 and the hole 32 in column 3 were punched by punching members in the same station, as, for example, station ll. The hole 33 in column 2 and the hole 34 in column 4 were .punched by punching members in, for example, station 2. Thus, it may be seen that by providing two separate punching stations, the problem of spacing the various punching members is greatly simplified. In the arrangement of the punching members in the die construction 36 for station 1 and the die 37 for station 2, Figure 4, each alternate column, 1, 3, 5, etc., is formed by the punching members in station 1, whereas the intermediate columns 2, 4, 6, etc., are formed by the punching members in station 2. Each column contains l2 punching members and there are 40 columns of punching members in each of the two stations. This permits the punching of 960 separate holes by the particular apparatus illustrated in the drawings. It will now also be obvious that by having two separate stations which are substantially identical the apparatus Will require a multiplicity of identical parts instead of the more expensive multiplicity of diflerent parts.

Since both of the punching stations are substantially identical, the following description will be simplified by describing only one station.

Referring now to Figures 2 and 3 of the drawings, a plurality of punching members, each beingidentified by the numeral 40, are positioned in a desired pattern as, for example, that shown in Figure 4 and described above. All of the punching members 40 are actuated by a common fluid pressure source which will now be described in detail.

Each of the punching members 40 bears against or, if desired, is attached to an actuating piston 41 which is slideably mounted in a cylinder 42. One end of each cylinder 42 is communicated with a fluid-containing manifold 45 by means of a channel 46. A valve 47 is positioned to normally close each of the channels 46 when in the position shown inFigures 2 and 3. The opening of selected valves 47, therefore, determines the actuation of each associated punching member as pressure is applied to the fluid in the manifold 45.

It should be noted that the actuating fluid in the manifold 45 does not experience any appreciable flow but, rather, is subjected to repeated cycles of pressure applied and released at a rapid rate. Therefore, it is essential that the selection of punching members to be actuated and the opening of the valve 47 associated with each selected punching member must be at the same rapid rate.

To accomplish this rapid control of the valves 47 in the embodiment of the invention illustrated in the drawlngs, each valve 47 has a portion 48 which extends across the manifold 45 and terminates in a piston portion 49. As each piston portion 49 moves in its respective cylinder 50, the valve 47 associated with it will open and 1 close.

A chamber 51 formed in each cylinder 50 behind each piston portion 49 encloses a fluid to which pressure is applied and released by communication through a channel 52 with a control fluid in a manifold 53. Pressure is applied and released to this, control fluid in a timed relation with the cycle on the actuating fluid in the manifold 45. This pressure cycle will be described in greater detail presently.

The channel 52 is normally closed by a valve 54 having anextension 55 against which a compression spring 56 maintains a biasing force. Also attached to each extension 55 by means of a rod- 57 is an arm 58 of an electromagnetic device 59. One physical arrangement of 4 the electromagnetic devices 59 is shown in Figure 3 for illustration purposes only. Now, as pressure is applied to the control fluid within the manifold 53, all of the valves 54 are forced open against the action of the respective coil springs 56. If it is desired that a particular punching member be actuated, the electromagnetic device 59 associated with that punching member will be energized to hold open the valve 54 to which it is connected.

Pressure to the actuating fluid and to the control fluidis alternately applied and released according to a timed cycle. It is essential to note, as mentioned previously, that there is no appreciable fluid flow, it being only necessary to apply and release pressure on the existing fluid. Any suitable apparatus may be used to accomplish the desired pressure and release cycle. One apparatus is illustrated diagrammatically'in Figure 2. According to this illustration, a conduit 61 communicates the actuating fluid in the manifold 45 with a chamber 62 in a housing 63. A piston member 64 with enlarged portions 66, 67 and 68 is adapted to be reciprocated against a compression spring 69 by a rotating cam 70. With the piston member64 in the position shown, the actuating fluid in the manifold 45, the conduit 61, and the chamber 62 is vented to a reservoir 71 through conduits 72 and 73.

With the cam 7 0 rotated 180 such that the piston member 64 is in its full upward position, the enlarged portion 66 Will seal ofi the pressure relief conduits 72 and 73 and, at the same time, the enlarged portion 67 will open the fluid pressure conduit 76 to the chamber 62. Pressure is supplied through the conduit 76 by a fluidpump 77 driven by a motor 78 and a shaft 79. Thus, as the piston member 64 is reciprocated, pressure to the fluid in the manifold 45 is alternately applied and released.

The reciprocating piston member 81 in the housing 82 operates in substantially the same manner as that just described. A cam 83 rotates 'to reciprocate the piston member 81 against a compression spring 84 such that enlarged portions 86 and 87 alternately connect a pres sure conduit 88 and a relief conduit 89 to a conduit 91 leading to the manifold 53. Pressure is supplied to the fluid in the conduit 88 by a fluid pump 92 connected to a the motor 78 by a shaft 93.

Pressure to thu fluid is. maintained by pressure control units 94 and 95 interposed in the pressure conduits 76 and 88, respectively. With this arrangement, the principal flow of fiuid is from the reservoir, through the fluid pumps, through the pressure control unit, and back to the reservoir. A relatively constant fiuid pressure head is maintained in the conduit .88 and in the conduit 76 for actuation of the control valves and the punching members, respectively. 7

In the embodiment of the invention shown in the drawings, the return of the punching members 40 which have been actuated is provided by a plurality of spaced apart bail bars extending the length of each row. As shown inFigure 3, there are 12 bail bars for each punch station. Each of these bail bars 100 is substantially L- shaped in cross section such that a portion 101 extends into a slot 102 in each of the punching members 40 along the length of the bar. All of the bars 100 are connected together bymembers 103 and 104, Figure 2, such that they may be actuated in unison.

During each pressure cycle on the actuating fluid in the ,manifold 45, pistons 106 and 107 are moved upwardly due to the pressure of the fluid communicated to each piston through conduits 108 and 109, respectively ,Any punching member 40' not to be actuated during a particular cycle Will be unaffected by this movement of -.the bail bars because eachslot 102 is elongated as shown in Figure 3. The upper pistons 111 and 112 will present no resistance to this movement because the conduits 113, and 114 are vented to the reservoir 71 during this portion of the cycle. p I 7 After the pressurecycle is completed, the manifold, 45

answer is vented to-tlie reservoir to relieve the pressure developed therein and, at the same time, pressure is applied to the fluid in the conduits 113 and 114. With pressure now supplied to the pistons 111 and 112, the bail bars 100 will be forced to their downward position, returning all raised or actuated punching members 40 to the positions shown in the drawings.

Due to the high speed operation of an apparatus constructed in accordance with the present invention, provision is made for removing the material punched from the cards by the punching members 40 and which accumulates in a chamber 115. Of course, it is understood that any suitable means may be provided to accomplish this purpose, the one shown being merely exemplary. To keep the chamber 115 cleared in the embodiment of the invention shown in the drawings, a conduit 116 connects the chamber 115 to a vacuum system which may, if desired, be operated by the motor 78. The punched waste material is then collected in a suitable receptacle (not shown) for easy disposal.

A detailed description of one cycle of operation for an apparatus constructed in accordance with the principles of the invention will present a better understanding of the inter-relationship of the various component parts. As unpunched cards from the magazine 12 are fed successively at a rapid rate into the punch apparatus 10, each card is momentarily halted first in station 1 and then in station 2. In each of these stations, holes are punched at predetermined locations in each card to represent various information.

While a card is being moved into position against the positioning member 38, Figure 1, the cam 83, Figure 2, moves the piston member 81 to connect the fluid pressure conduit 88 through the conduit 91 to the control fluid in the manifold 53. The fluid pressure developed in the manifold 53 opens all of the valves 54 to apply pressure to the fluid in chambers 51. Coincident with this operation, information as to which of the punching members 40 are to be actuated is supplied to selected electromagnetic devices 59 as, for example, from any suitable computer device. This information is in the form of an electrical current pulse which energizes the selected electromagnetic devices.

As the cam 83 continues to rotate, the piston member 81 moves to close the pressure conduit 88 and to vent the fluid pressure in the manifold 53 through the conduits 91 and 89 to the reservoir 71. With the pressure thus relieved on the fluid in the manifold 53, the various compression springs 56 will close the valves 54 trapping the pressurized fluid in the chambers 51. However, those valves 54 associated with the electromagnetic devices 59 which have been energized by an information current pulse will be kept open due to the attraction of the arms 58 overcoming the force of the biasing compression spring 56.

The cam 70, being in timed relation with the cam 83, now moves the piston member 64 to connect the fluid pressure conduit 76 to the chamber 62 and, by means of a conduit 61, to the manifold 45. Fluid pressure in the manifold 45 will not be able to move the pistons 49 downwardly due to the trapped pressurized fluid in the chambers .51 and,- thus, the valves 47' associatedwith these pistons will remain closed. However, selected valves 54 are being held open by their respective electromagnetic devices 59. The pistons 49 associated with these valves 54 will be moved downwardly by the fluid pressure in the manifold 45, which movement also opens the valves 47 to which these pistons 49 are connected.

Upon the opening of any valve 47, pressure on the fluid. in the manifold 45 is communicated through the channel 46 to actuate the piston 41 and its associated punching member 40.

As pressure is applied to the fluid in the manifold 45, it is transmitted to the lower bail pistons 106 and 107 through the open channels 108" and 109, respectively.

The upward movement of these lower bail pistons moves 1 the bail bars upwardly such that the portions 101 are at the top of the slots 102 in the punching members 40 which are not actuated and at the bottom of the slots 102 in the punching members 40 which are actuated.

The continually rotating cam 70 now moves the piston member 64 to close off the pressure conduit 76 and vent the manifold 45 to the reservoir 71 through the conduits 61, 72 and 73, at the same time, pressure is applied to the fluid in the conduits 113 and 11-4 to move the upper bail pistons 111 and 112 downwardly. The downward movement of the pistons 111 and 112 acts to return the bail bars 100 and the actuated punching members 40 to the position shown in the drawings. At this point, the cam 83 is again in position to repeat the application of pressure to the control fluid in the manifold 53. As mentioned above, when pressure is developed on the fluid in the manifold 53, all of the control valves 54 are opened and any actuating valve 47 which has previously been opened is now closed by the upward movement of the associated piston 49. Then the punching cycle just described is repeated.

In Figure 5 of the drawings, the relative timing of the various components of the apparatus is shown as well as the approximate displacement for each of these parts. The overall time for one cycle is only in the order of 30 milliseconds with the actual punching operation consum-' ing only approximately 6 milliseconds.

The invention may be embodied in other specific forms without departing from the essential characteristics thereof. Hence, the present embodiment is therefore to be considered in all respects merely illustrative and not as being restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all modifications and variations as fall within the meaning and purview and range of equivalency of the appended claims are therefore intended to be embodied therein.

I claim: 1. A high speed punch apparatus comprising a plurality of punching members, fluid pressure actuating means in common with all of said punching members, a first valve means to connect each of said punching members and said fluid pressure actuating means, a plurality of separately operable electromagnetic means, and a second valve means connected with each of said electromagnetic means such that the actuation of a selected electromagnetic means actuates a predetermined second valve means to apply automatically said fluid pressure actuating means to the'respective punching member through the respective first valve means.

2. A high speed punch apparatus comprising a plurality of punching members, fluid pressure actuated piston means associated with each of said punching members, an enclosed manifold to contain a fluid, means to alternately apply and release pressure to said fluid, channel means communicating each of said piston means with said manifold, valve means associated with each of said channel means to normally maintain each channel means closed, an electrical winding means corresponding to each of said valve means, and fluid means to maintain automatically in an open position for one cycle of operation only the respective valve means for predetermined ones .of said electrical winding means which are actuatedv ac cording to a selected schedule.

3. A high speed punch apparatus comprising a plurality of punching members, fluid pressure actuated piston means associated with each of said punching members,

an actuating fluid capable of being pressurized to actuate said piston means, means to alternately apply and release pressure to said actuating fluid according to a predetermined timing cycle, channel means communicating each of said fluid pressure actuated means with said actuating fluid, valve means associated with each of said channel aesaasv means to normally maintain each channel means closed, actuating fluid means to open automatically said valve means according to a schedule timed with said pressure cycle, and electromagnetic means to hold open predetermined ones of said valve means to permit said actuating fluid to actuate the associated punching member.

4. A high speed punch apparatus comprising a plurality of punching members, fluid pressure actuated piston means associated with each of said punching members, an actuating fluid capable of being pressurized to actuate each of said piston means, means to alternately apply and release pressure to said actuating fluid according to a predetermined timing cycle, channel means communicating each of said fluid pressure actuated means with said actuating fluid, valve means associated with each of said channel means to normally maintain each channel means closed, an extended portion on each of said valve means, and a source of control fluid adaptable to be pressurized according to a schedule timed with said timing cycle, said extended portion being in communication with said control fluid such that said valve means is closed when said control fluid is pressurized, and an electrically controlled valve means to release the fluid pressure against predetermined ones of said extended portions such that a selected valve means will be open during a pressure cycle of said actuating fluid.

5. A high speed punch apparatus comprising a punching member, fluid pressure actuated means associated with said punching member, a source of actuating fluid, means to apply and release pressure on said actuating fluid according to a predetermined schedule, a valve means interposed between said fluid pressure actuated means and said source of actuating fluid, an extended portion on said valve means, a piston means forming a part of the end of said extended portion opposite the valve means, a source of control fluid in communication with said piston means, means to apply and release pressure on said control fluid, and control valve means for communicating said control fluid with said piston means in timed relation with said predetermined schedule.

6. A high speed punch apparatus for providing holes in record cards at predetermined positions, comprising a plurality of punching members, fluid pressure actuated means associated with each of said punching members, a first manifold for containing an actuating fluid, means to apply and release pressure on said actuating fluid in a timed cycle, channel means to communicate said actuating fluid with each of said fluid pressure actuated means, a first valve means to maintain each of said channel means normally closed, a second manifold for containing a control fluid, a second valve means interposed between said flrst valve means and said control fluid, means to communicate said control fluid with said second valve means, means to apply and release pressure on said control fluid in timed relation with the timed cycle on said actuating fluid, and electrical bias means to maintain predetermined ones of'said second valve means in an open position during a pressure cycle of said actuating fluid.

7. The high speed punch apparatus of claim 6 wherein said plurality of punching members includes a first group and a second group, and said first and second groups being positioned such that the punching members of said 7 second group operate to provide holes in the record cards intermediate of the holes provided by said first group.

8. The high speed punch apparatus of claim 6 wherein said actuating fluid and said control fluid in said first and said second manifolds, respectively, are supplied from a common reservoir.

9. Hydraulic apparatus comprising, a manifold operably containing fluid, means to apply and then release pressure on said fluid, means providing a channel for flow of fluid from said manifold to a utilization device, a valve adapted to open and close said channel to said flow when said valve is at opened and at closed posi- 8 tions, respectively, said valve being responsive to applying of pressure to fluid in said manifold to be urged by such fluid to opened position, valve position determining means adapted when said valve is so urged to selectively provide one at a time of the actions of locking said valve in closed position against such urging and of permitting such urging to move said valve to opened position, and means to render said valve in closed position prior to said applying of pressure.

10. Hydraulic apparatus comprising, a manifold operably containing fluid, means to apply and then release pressure on said fluid, means providing a channel for flow of fluid from said manifold to a utilization device,

a valve adapted to open and close said channel to said,

flow when said valve means is at opened and at closed positions, -respectively, said valve being responsive to applying of pressure to said manifold to be urged by such fluid to opened position, valve position control means adapted when said valve is so urged to lock said valve in closed position against such urging, selectively operable means adapted when operated to negate the locking action of said control means to thereby permit such urging to move said valve to opened position, and means to render said valve in closed position prior to said applying of pressure.

11. Apparatus as in claim 10 in which said control means comprises, dashpot means having a fluid escape port and connected to said valve to permit movement thereof from closed to open position only when said port is open, and a port valve which is biased to normally close said port but which is adapted to be maintained in open position by the operation of said selectively operable means.

12. Apparatus as in claim 11 in which said port valve is spring biased.

13. Apparatus as in claim 10 in which said selectively operable means is an electromagnet.

14. Hydraulic apparatus comprising, a manifold operably containing fluid, means to apply and then release pressure on said fluid, means providing a channel for flow of fluid from said manifold to a utilization device, means providing across said manifold from said channel a cylindrical recess communicating with said manifold, a valve member disposed in said manifold between said channel and recess and having at opposite ends a head providing a valve for said channel and a piston received within said recess, said piston upon the applying of pressure to the fluid in said manifold being urged by such fluid to move said head from a channel-closing position to a channel-opening position, and means adapted by controlling the pressure on the side of said piston away from said manifold to'select'ively preclude or permit such movement of said head.

15. Apparatus as in claim 14 in which a hydraulic chamber is formed by said piston and the portion of said recess disposed inwardly of said piston, and in which said controlling means comprises, means providing a conduit connecting said chamber with a reservoir of control fluid, a lift valve adapted when seated to close said conduit, means to bias said lift val-ve so as to normally maintain it seated, means adapted by applying pressure to said fluid in said reservoir before pressure is applied to the fluid in said manifold to raise said lift valveofi its seat to thereby produce from said reservoir to said chamber a flow of control fluid which impels said piston to the position at which said head closes said channel, and means selectively operable thereafter to maintain said lift valve in raised position so as to permit the applying of pressure to the fluid in the manifold to move said piston to expel fluid from said chamber through said port, said piston thereby moving said head from said channel-closing to said channel-opening po- 7 sition.

16. Hydraulic-apparatus comprising, a manifold oper ably containing actuating fluid, means forming a by draulic cylinder communicating with said manifold, means providing a reservoir for control fluid, means defining a conduit for flow of control fluid between said reservoir and the inner end of said cylinder, a piston disposed in said cylinder between the inner end thereof and said manifold to form with said cylinder a hydraulic chamber on the inward side of said piston, said chamber being adapted to be filled through said conduit with control fluid from said reservoir, means to apply pressure to said actuating fluid in said manifold to thereby urge said piston towards the inner end of said cylinder, and means to selectively preclude or permit expulsion of control fluid from said chamber through said conduit by said urged piston to thereby disable and enable, respectively, said piston from moving inwardly in response to such urging.

17. Hydraulic apparatus comprising, a manifold operably containing actuating fluid, means forming a hydraulic cylinder communicating with said manifold, means providing a reservoir for control fluid, means defining a conduit for flow of control fluid between said reservoir and the inner end of said cylinder, a piston disposed in said cylinder between the inner end thereof and said manifold to form with said cylinder a hydraulic chamber on the inward side of said piston, means adapted by applying pressure to said control fluid in said reservoir to produce from said reservoir through said conduit and into said chamber a flow of control fluid which impels said piston toward said manifold, means adapted by thereafter applying pressure to said fluid in said manifold to urge said piston inwardly, and means operable at that time to selectively preclude or permit expulsion of control fluid from said chamber through said conduit by said urged piston to thereby disable and enable, respectively, said piston from moving inwardly in response to such urging.

18. Hydraulic apparatus comprising, a manifold operably containing actuating fluid, means forming a hydraulic cylinder communicating with said manifold, means providing a reservoir for control fluid, means defining a conduit for flow of control fluid between said reservoir and the inner end of said cylinder, a piston disposed in said cylinder between the inner end thereof and said manifold to form with said cylinder a hydraulic chamber on the inward side of said piston, a lift valve adapted to close said conduit to flow of fluid therethrough when said valve is seated, means biasing said valve to normally maintain it in seated condition, means adapted by applying pressure to said control fluid in said reservoir to raise said valve against said bias oflt its seat to thereby produce a flow of control fluid from said reservoir through said conduit and into said chamber, and means selectively operable thereafter to maintain said lift valve in raised condition despite its bias.

19. Hydraulic apparatus comprising, a reservoir operably containing fluid, means providing a hydraulic chamher and, also, a conduit for flow of fluid between said reservoir and said chamber, a normally seated lift valve adapted when seated to close said conduit to flow of fluid therethrough, means adapted by applying pressure to fluid in said reservoir to raise said lift valve ofi its seat to thereby produce a flow of said fluid from said reservoir through said conduit into said chamber, and electromagnet means selectively operable thereafter to maintain said lift valve so raised.

20. Hydraulic apparatus comprising, a reservoir operably containing fluid, means providing a hydraulic chamber and, also, a conduit for flow of fluid between said reservoir and said chamber, a lift valve adapted when seated to close said conduit to flow of fluid therethrough, a spring applying to said lift valve a bias which normally maintains said valve seated, means adapted by applying pressure to fluid in said reservoir to raise said valve off its seat to thereby produce a flow of fluid from said reservoir through said chamber, said last-named means subsequently releasing such pressure to terminate such flow and to normally permit said spring to reseat said valve to thereby trap in said chamber the fluid which has flowed thereinto, and electromagnet means which is selectively operable upon such pressure release to maintain said valve raised to thereby permit return of fluid from said chamber through said conduit to said reservo1r.

References Cited in the file of this patent UNITED STATES PATENTS 698,104 Clark Apr. 22, 1902 1,978,966 Sprague Oct. 30, 1934 2,062,456 Johnstone Dec. 1, 1936 2,078,470 Thomas Apr. 27, 1937 

